In some digital integrated circuits, small signals such as of the ECL level are transmitted based upon a power source voltage VCC such as GTL (gunning transceiver logic) or +5 V in order to transmit signals at high speeds over a signal transmission line and to decrease the consumption of electric power. The GTL has been disclosed in ISSCC, International Solid State Circuit Conference, Feb. 19, 1992, pp. 58-59.